LUX-ZEPLIN (LZ) Status. Attila Dobi Lawrence Berkeley National Laboratory June 10, 2015 WIN Heidelberg

Transcription

1 LUX-ZEPLIN (LZ) Status Attila Dobi Lawrence Berkeley National Laboratory June 10, 2015 WIN Heidelberg 1

2 LZ = LUX + ZEPLIN 29 institutions currently About 160 people Continuing to expand internationally LIP Coimbra (Portugal) MEPhI (Russia) Edinburgh University (UK) University of Alabama University at Albany SUNY Berkeley Lab (LBNL), UC Berkeley Brookhaven National Laboratory Brown University University of California, Davis Fermi National Accelerator Laboratory Lawrence Livermore National Laboratory University of Maryland Northwestern University University of Rochester University of California, Santa Barbara University of South Dakota South Dakota School of Mines & Technology University of Liverpool (UK) South Dakota Science and Technology Authority Imperial College London (UK) SLAC National Accelerator Laboratory University College London (UK) Texas A&M University of Oxford (UK) Washington University STFC Rutherford Appleton, and Daresbury, Laboratories University of Wisconsin (UK) University of Sheffield (UK) Yale University 2

3 LZ Timeline Year Month Activity 2012 March LZ (LUX-ZEPLIN) collaboration formed May First Collaboration Meeting Septembe DOE CD-0 for G2 dark matter experiments 2013 rnovember LZ R&D report submitted 2014 July LZ Project selected in US and UK 2015 April DOE CD-1/3a approval, similar in UK Beginning procurements(xenon, PMT, cryostat) 2016 April DOE CD-2/3b approval, baseline, all fab starts 2017 June Begin preparations for surface SURF 2018 July Begin underground installation 2019 Feb Begin commissioning 3

4 Sanford Underground Research Facility in South Dakota Davis Cavern 1480 m (4300 mwe) LZ in LUX Water Tank LUX to be removed by early 2017 Water tank kept 4

5 Scale Up 50 in Fiducial Mass LZ Total mass 10 T WIMP Active Mass 7 T WIMP Fiducial Mass 5.6 T LUX 5

6 LZ Overview 6

7 Xe Detector 247 PMT 180 total Skin PMT 241 PMT 7

8 Xe Detector PMTs R PMTs for TPC region Extensive development program, 50 tubes in hand, benefit from similar development for XENON1T, PANDA-X and RED Materials ordered and radioassays started prior to fabrication. First production tubes early Joint US and UK effort R for skin region 8

9 Yale High Voltage Studies Reverse field region cathode grid 3 RFR rings (half height) Ground grid IC London Testing for cathode HV at Yale moving to LBNL and Berkeley. Also development at IC London. Cathode voltage Design goal: 200 kv LZ nominal operating goal: 100 kv (750 V/cm) Feedthrough prototype tested to 200 kv (Dielectric Sciences 2077) 9

10 Cryostat Vessels UK responsibility Low background titanium chosen Ti slab for all vessels(and other parts) received and has been assayed Contributes < 0.05 NR+ER counts in fiducial volume in 1,000 days after cuts 10

11 85 Kr Removal and Screening Remove Kr to <15 ppq (10-15 g/g) using gas chromatography. Best LUX batch 200 ppq Setting up to process 200 kg/day at SLAC Have a sampling program to instantly assay the removal at SLAC and continuously assay in situ LUX Xenon Sampling 11

12 LZ Calibrations Demonstrated in LUX. Calibrate The Signal and Background Model in situ. DD Neutron Generator (Nuclear Recoils) Tritiated Methane (Electron Recoils) Tritium Beta Spectrum Measured in LUX H T C H H Monochromatic 2.5 MeV neutrons 12

13 Background Modeled Just LXe TPC Use LXe skin, Outer Det. Fid. Mass 3.8 T Fid. Mass 5.6 T 2.2 bkg events, 1,000 days 13

14 Projected Sensitivity Spin Independent (LZ 5.6 Tonnes, 1000 live days) projected cm 2 Excellent projected sensitivity limited by neutrinos only. 14

15 Other Physics Axions Effective Field Theory Interaction Decomposition Neutrinoless Double Beta Decay ~600 kg of 136 Xe in active volume 2-5x10 26 year half life Neutrino Physics Coherent neutrino-nucleus scattering Solar Supernova 15

16 Coherent ν-nucleus Scattering v sum LZ may be the first to observe coherent neutrinonucleus scattering 8 B Recoils mimic low mass WIMPs WIMP Search 3-30 kev Expect ~10 8 B events and 0.5 events from others DSN and atmospheric neutrinos will become the dominant background for experiments beyond LZ. 16

17 ν-electron Scattering -The dominant background With 99.5% electron recoil rejection (at 50% nuclear recoil acceptance) Electron recoils from 85 Kr, 222 Rn and PMTS are less than 10% of PP solar neutrino rate Wimp Search kevee (and before 99.5% electron recoil rejection) ~270 PP solar events ~40 2vBB Improve measured solar neutrino luminosity to <5% from 10% 17

18 Conclusions LZ Project well underway, with procurement of Xenon, PMTs and cryostat vessels started along with prototype and assay programs LZ benefits from the excellent LUX calibration techniques and understanding of background LZ sensitivity expected to be finally limited by neutrino-induced `background 18

19 Extra Slides 19

20 Xe Detector Prototyping Extensive program of prototype development underway Three general approaches Testing in liquid argon, primarily of HV elements, at Yale and soon at LBNL Design choice and validation in small (few kg) LXe test chambers in many locations: LLNL, Yale-> UC Berkeley, LBNL, U Michigan, UC Davis, MEPhI System test platform at SLAC. Phase I about 100 kg of LXe starting soon with complete prototype TPC 20

21 Design Status Summary Conceptual, and in some cases more advanced design, completed for all aspects of detector Conceptual Design Report to appear on arxiv Acquisition of Xenon started Procurement of PMTs and cryostat started Collaboration wide prototype program underway to validate design Backgrounds modeling and validation well underway 21

22 Tritiated-Methane, The Ideal ER Calibration Source Methane diffuses much slower than bare tritium. Dissolved uniformly in the xenon. Removed with standard purification technology. Used to calibrate the fiducial volume. LUX (2013) WIMP Search Single Scatter ER events in energy region of interest: 0.1 kev to 18 kev Mean energy: 5 kev Peak energy: 2.5 kev T H C H April APS 2015 Attila Dobi H 22

23 Adelphi DD108 Neutron Generator Installed Outside LUX Water Tank log 10(cts / µs / cm) Drift time [µs] Approximate fiducial for yield measurements LUX Preliminary James Verbus - Brown University y Distance into LXe [cm] 50 This cut eliminates shine from passive materials and ensures 95% of neutrons in beam sample have energy within 4% of 2.45 MeV The mean energy of neutrons produced at 90 by the DD108 was measured to be 2.45 ± 0.05 MeV at Brown University o APS April Meeting - April 12th, 2015

24 LZ Underground at SURF Years of experience at SURF from LUX Control room LN storage room LZ detector inside water tank Xenon storage room 24

25 Sensitivity with SUSY Theories 25

26 Sensitivity with Competition 26

27 Response of Xe to Neutrinos arxiv: 1307:

28 LZ At the neutrino `knee arxiv: LUX Xenon 1T LZ After LZ, extremely large detectors would be needed. 28

29 29

30 Spin Dependent Neutron 30

31 Spin Dependent Proton 31

32 Time Evolution Ge, NaI no discrimination Ge, w/discrim. ZEPLIN-III LXe, w/discrim. LUX LZ cm 2 XENON 1T 32